How is this chain of volcanic islands forming? Tectonic plates are sliding past each other, generating magma, which creates a volcano. Two tectonic plates are pulling apart, creating magma through decompression melting. A tectonic plate is moving over a mantle plume, which burns through the plate to create a chain of volcanoes. A tectonic plate is being subducted and partially melted, producing magma that rises to create a volcanic chain.

A tectonic plate is moving over a mantle plume, which burns through the plate to create a chain of volcanoes.

Explanation:

For a chain of volcanic islands to form, it is necessary for the tectonic plates to move on top of a mantle plume, thus creating a "cord" of islands, forming the chain of volcanic islands.

A plume mantle is also called a hot spot and is formed by a geological thermal aanomalia, which pulls the magma from the deepest layers to the surface.